Built in functions in Python

What are built-in functions 🔝

How to List All Built-in Functions in Python 🔝

Python provides built-in tools to dynamically inspect the current scope and see all functions available out of the box. You can quickly list all built-in functions using Python's dir() function on the built-in scope.

1. Using dir(__builtins__)

The fastest way to list built-in functions is by using the __builtins__ object directly in your code:

print(dir(__builtins__))

2. Importing the builtins Module

You can also explicitly import the standard builtins module to retrieve the list:

import builtins

print(dir(builtins))

Filtering Callable Functions Only

Running dir(builtins) returns everything in the built-in namespace, including internal attributes (like __name__), constants (like True and False), and built-in exceptions (like ValueError).

To extract only callable functions while excluding internal dunder methods and constants, you can use a list comprehension with callable():

import builtins

# Filter out internal dunder attributes and select callable functions
builtin_functions = [
    name for name in dir(builtins) 
    if callable(getattr(builtins, name)) and not name.startswith("__")
]

print(builtin_functions)

import builtins
for i in dir(builtins):
    print(i)
print("Total Builtin Functions : ",len(dir(builtins)))

Total Builtin Functions :  158

Checking if a word is Built-in function or not

import builtins
if 'sum' in dir(builtins):
    print(' sum is a built-in function' )
else:
    print(' No it is not a built-in function')

 sum is a built-in function

Can I use builtin functions as variable names ?

Naming Conflicts and Overriding:

Examples

#int=225 # this line will override the built-in function int()
x=int(input('Enter a number : '))
print(x*2)

#True=50 # reserved words as variables are not allowed
x=sum([5,7]) # sum is a built-in function
sum=50 # Use of Built-in functions as variables allowed
#x=sum([6,7])
print(sum)

How to avoid using built-in functions and reserved words ?

• Choose names that reflect the variable's content or purpose.
• Explain what the variable holds, making your code self-documenting.
• Avoid ambiguous names like x, temp, or data.
• Instead, use names like first_name, total_price, or average_score.

Built-in Functions vs. Standard Library vs. Third-Party Modules 🔝

A common point of confusion for beginners is understanding why some functions are directly available while others require an import statement or external installation. In Python, tools are categorized based on how they are loaded into memory:

• Built-in Functions: Functions like len(), print(), type(), and range() are loaded automatically into Python's global namespace whenever your script or environment runs. You do not need to use an import statement to use them—they are ready to execute out of the box.
• Python Standard Library: Modules such as math, os, datetime, and sys come pre-installed with every standard Python download. While they do not require extra installation via pip, you must explicitly write import math or import os before using their functions. This keeps Python lightweight by loading specialized tools only when needed.
• Third-Party Libraries: External packages like pandas, numpy, requests, or matplotlib are not included with default Python installations. To use them, you must install them into your environment first using a package manager like pip install pandas, and then load them using import pandas as pd in your code.

Understanding Built-in Items vs. Callable Functions 🔝

When you inspect Python's default environment using dir(__builtins__), Python returns a list of approximately 160 items. However, not every item in this list is a standard function that takes inputs and performs an action. Instead, the __builtins__ module contains a mix of functions, exception handlers, system constants, and internal properties.

To separate executable tools from static attributes, we use Python's callable() function. Filtering the list using callable() yields around 146 callable built-ins. Here is how the full list breaks down:

• Callable Functions (~146 items): These are items you can execute using parentheses (). They include core utility functions like len(), print(), and sum(), as well as built-in type constructors like int(), str(), list(), and dict().
• Built-in Exceptions & Errors: Standard exception classes like ValueError, TypeError, ZeroDivisionError, and FileNotFoundError are defined within the built-ins module so Python can handle errors across all scripts without requiring additional imports.
• Constants & Internal Attributes: Static values and metadata like True, False, None, __name__, and __doc__ reside in the built-ins namespace. Since these are fixed values or properties rather than executable logic, passing them to callable() returns False.

By using [item for item in dir(__builtins__) if callable(getattr(__builtins__, item))], you can programmatically extract only the active, callable tools available in your Python environment.

What is Vanilla Python? 🔝

The term "Vanilla Python" refers to writing Python code using only standard, unadorned language features—specifically built-in functions, native data structures, and modules provided by the standard library. When a project is written in Vanilla Python, it means it runs cleanly without relying on any third-party packages installed via pip.

Understanding Vanilla Python is essential before adopting external frameworks. It ensures your code remains fast, lightweight, and free from external dependency management issues or unexpected updates from third-party packages.

Comparing Built-in, Standard Library, and Third-Party Functions 🔝

• Python built-in functions , listing all and checking #python #pythonbasic
  15-Feb-2024

Questions 🔝

Subhendu Mohapatra

Author

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